There are an estimated 11 million diabetics in the United States. Of these 11 million diabetics, approximately 3 million are Type I diabetics who are insulin dependent and require an average of 11/2 shots of insulin per day. The insulin must be injected in measured doses, as determined by a physician, in order to establish an appropriate concentration of insulin in a person's system. Since insulin is a protein which is broken down by gastrointestinal enzymes, it must be introduced to a person's system by injection. The most common means for injection is a syringe having an attached needle for puncturing the skin of the person so that the insulin can be injected into the tissues beneath the skin. Thus, each injection causes a puncture wound and resulting pain and discomfort. For a large number of persons, the daily (or more often) ordeal of injecting the insulin, although necessary, is practically intolerable. Thus, a need exists for an alternative means for injecting the insulin through the skin without puncturing the skin.
Numerous devices have developed in the injection art for injecting liquid medication directly through the skin of a person without requiring a needle or other apparatus for piercing or puncturing the skin. These needleless injection systems use a source of high pressure to force the liquid medication directly through the skin. Almost everyone is familiar with the high volume devices used by the military to inoculate servicemen en masse and used by various public health services to inoculate the general public as a means for preventing epidemics. The instruments used for these purposes are typically quite bulky, have a large reservoir for storage of the liquid medication, and are intended to be operated by trained personnel. The instruments are quite expensive and are unattractive for the daily use by one person for insulin injections or injections of any other self-administered medication.
Various other devices appear in the injection art which are intended to provide individualized needleless injections. Some early examples are U.S. Pat. Nos. 2,547,099 and 2,605,763 to Smoot; U.S. Pat. No. 2,645,223 to Lawshe; U.S. Pat. No. 2,635,601 to May; and U.S. Pat. No. 3,688,765 to Gasaway. The apparatuses described in the foregoing patents have limitations which appear to have reduced or prevented the widespread use of these devices by individuals. Thus, a need continues to exist for a low-cost needleless inoculation system which is safe, economical and easy to use.